Unable to SCP since upgrade to Ventura

Since the upgrade to macOS 13 Ventura, all my attempts to use scp from the command line have failed with this error message:

subsystem request failed on channel 0
scp: Connection closed

I was previously able to do so successfully, so this is not a server problem. I had to update my SSH config to work with my old RSA keys, and SSH login works without a problem now. Why can't I copy files?